MINOR: Update rocksDB dependency to 4.9.0

rocksdbjni version 4.9.0 now includes support for running on Windows; this PR updates Kafka Stream's dependency to that version.  Tests pass locally, except for a timeout in testReprocessingFromScratchAfterReset that doesn't seem related; it happens with and without this change.

This contribution is my original work and I license the work to the project under the project's open source license.

Author: Mathieu Fenniak <[email protected]>

Reviewers: Ismael Juma <[email protected]>

Closes apache#1783 from mfenniak/update-rocksdb-4.9

Author: repl-mathieu-fenniak

gradle/dependencies.gradle

@@ -38,7 +38,7 @@ versions += [
   metrics: "2.2.0",
   powermock: "1.6.4",
   reflections: "0.9.10",
-  rocksDB: "4.8.0",
+  rocksDB: "4.9.0",
   scalaTest: "2.2.6",
   scalaParserCombinators: "1.0.4",
   scoverage: "1.1.1",